A submersible pump assembly for downhole use. The invention relates to a submersible pump assembly as defined in the preamble of claim 1.
A submersible pump assembly of the generic kind defined is known from U.S. Pat. No. 3,677,665. It comprises a motor, an equalizer, a gear transmission, and a pump, especially an eccentric worm type pump. The motor drives an input shaft of the gear transmission, the output shaft of which drives a rotor of the eccentric worm type pump. The submersible pump assembly is lowered into a well, with the motor disposed at the lower end of the submersible pump assembly, as seen from ground level. The eccentric worm type pump, thus located at the upper end of the submersible pump assembly, conveys into a casing which leads up to ground level. The gear transmission has at least one transmission step in order to step down the rotational speed of the motor to a reduced rotational speed of the pump rotor. This transmission step is cooled and lubricated by a cooling and lubricating fluid. Cooling and lubricating fluids are used also within the eccentric worm type pump or the motor in order to distribute the heat due to energy losses originating in the motor and/or to diminish wear of movable components within the eccentic worm type pump. The equalizer functions to adapt the lubricating fluid pressure to ambient pressure. It is arranged between the gearing and the motor, has its own housing, and is connected in such a way to the gearing and the motor that a pressure balance can be obtained between the lubricating fluids. This does not involve any exchange of lubricating fluid worth mentioning.
The structural units of submersible pump assemblies of the kind defined, such as the motor, the gear transmission, or the pump, each have their own housing of which the diameter is much smaller than the length thereof. The heat due to energy loss has its origin in a limited area, such as the transmission step, for example. Therefore, it is distributed only insufficiently in the elongate housing of the known submersible pump assembly of the kind in question.
It is known from DE 35 09 023 C2 and U.S. Pat. No. 3,794,447 to use a screw thread type pump as the pumping means for conveying lubricating fluids, such a pump comprising at least one conveying thread to generate a flow of fluid in the direction of the axis of rotation of the pump rotor.
A slide ring seal, including a screw thread type pump for the circulation of a cooling, lubricating, or blocking medium is known from DE 19 13 397 C3. It serves to seal a shaft passage aperture in a housing and causes the contact pressure of a slide ring to vary in response to the rotational speed and direction of the shaft to be sealed.
It is the object of the invention to improve a submersible pump assembly of the kind defined such that the heat due to energy loss generated in the pump is distributed more evenly.
The object is met, in accordance with the invention, by the features recited in claim 1.
The provision according to the invention of the equalizer makes it possible for the heat resulting at the transmission step to be distributed directly in the lubricating fluid volume of the equalizer and to be transmitted additionally to the surroundings by the outside surface thereof.
The heat exchange is improved still further by the flow of lubricating fluid generated in the transmission step and in the equalizer, as recited in claim 2.
The provision of two pump means defined in claim 3 produces two lubricating fluid currents of which the individual flow resistance is reduced.
The embodiment according to claim 4 utilizes the centrifugal force which acts during rotation of the shafts on the co-rotating lubricating fluid. That enhances the flow of the lubricating fluid.
The further development described in claim 5 leads to mixing of the lubricating fluid of both flows within the spacing defined, thereby improving the heat exchange.
The further developments presented in claims 6 and 7 result in a particularly compact structure of the submersible pump assembly.
The design according to claim 8 permits the input shaft to be supported between the equalizer and the transmission step, and an exchange of lubricating fluid between the two to take place at the same time.
The arrangement of bearings in accordance with claim 9 provides improved lubrication of the shaft bearings.